A three-dimensional electron-density map of ∊16 calculated from 1590 (256 independent) strong reflections using the space group P1. (a), (b) and (c) are three-dimensional density maps viewed along the b, a and c axes, respectively. Four unit cells are outlined in (a). The symmetry elements can be identified from the density map, with mirrors perpendicular to the b and c axes (marked). The new origin is set on 2mm. The origin shifts obtained from the electron-density maps are Δx = 0, Δy = 0.25 and Δz = 0.15625. Banana-shaped clusters and pentagonal clusters21 are outlined in (a).